Detection devices can use a bead layer mounted on a support, wherein reagents are bonded to the beads to react with a sample. In many such devices, liquid flows perpendicularly into the layer so that flow occurring ACROSS the layer, such as could wash off beads inadequately adhered, is minimized.
However, in some environments, particularly qualitative detection of DNA, it is preferred that the sample liquid being analyzed flow-by, rather than through, the bead layer, for the desired reaction with the beads used for detection. In such a case, the flow-by of the liquid will wash off any beads that are not securely attached. If enough of the beads wash off, there will be insufficient numbers remaining to produce a visible signal that indicates the target DNA is present. For example, no color will generate even though the targeted DNA had been replicated or was present. It is possible to anchor beads against washoff, by using as their support, a latex-coated paper. However, the use of a paper support creates manufacturing disadvantages. The paper with the beads pre-attached must be carefully transported to the device's detection chamber, where it must be fixed in place. A more preferred method would be to somehow place the beads directly onto the material comprising the detection chamber, which can be polyethylene. This, however, has not been readily possible, since simply drying the beads in place on such a material, from an aqueous solution, provides insufficient anchoring of the beads when the sample to be detected flows by.
Accordingly, prior to this invention there has been a need to anchor detection beads to a support in a manner that is more convenient, that is, does not require an interim support other than the wall of the detection chamber.